Effects of cover on soil particle and associated soil nutrient redistribution on slopes under rainfall simulation

PurposeSediment detachment, transportation, and deposition occurred alternately along slope during erosion process. Nutrients were mobilized with sediment movement. In this research, nutrients and fractal characteristics were analyzed on both bare and covered slopes. Then, combined with photogrammetry technique, soil elevation and associated soil nutrient redistribution on slope positions during rainfall event were explored.Materials and methodsCombined with simulated rainfall method, bare and covered slopes experienced erosion process. Fractal theory was used to analyze sediment particle size distribution. Photogrammetry technique was applied to locate sediment redistribution. Soil and runoff were sampled and analyzed to obtain nutrient variations.Results and discussionCovered slope yielded less runoff and sediment in comparison to bare slope. Compared to bare slope, covered slope had lower total nitrogen (TN) (p=4.8x10(-24)) and total phosphorus (TP) (p=2.9x10(-23)) concentration but higher total organic carbon (TOC) concentration (p=9.6x10(-10)). There was no significant difference between inorganic carbon (IC) concentrations on bare slope and covered slope (p=0.051). Fractal dimensions ranged from 2.16 to 2.37 on bare slope, and they were greater than those from covered slope (ranged from 1.63 to 2.26). Linear and exponential relationships were established between fractal dimension and TOC, IC, TN, and TP concentrations. TOC concentration and IC concentration were in negative correlations with fractal dimension, while TN concentration and TP concentration were in positive correlations with fractal dimension. Mean elevation change analyzed from photogrammetry was -4.9 and -1.2mm on bare slope and covered slope, respectively. Upslope sections were main elevation and nutrient loss areas. 9.8mm soil lost on bare slope and 2.8mm on covered slope. TOC, IC, and TP concentrations decreased on upper position, while TN increased. Three sections in middle area had dramatic erosion variations and decreased TOC. Elevation increased on covered slope in F3 section. On downslopes, IC content increased whereas TOC concentration increased. TN and TP content decreased in most sections on the bare slope, while the situation was changed on the filter covered slope, and TN and TP accumulated on the middle slope.ConclusionsCover reduced runoff and sediment yield rates, and it also reduced elevation decrease degree. There was significant sediment deposition in the middle slope. Cover had functions in reducing TOC loss degree and preventing TN and TP loss out from the slope, but there was no significant difference between IC concentrations on bare slope and covered slope.